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Development of Automated Signal and Meta-dataQuality Assessment at the USGS
Advanced National Seismic System (ANSS)National Earthquake Information Center (NEIC)
D.E. McNamara, R. Buland, R. Boaz, H. Benz, L. Gee, W. Leith
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Broadband Stations Used by the NEIC~4,000 real-time channels~4,000 real-time channels
~450 stations~450 stationsANSS
IW
IMS
CDSN
GTSN
SLU
GSN
SNL
Weston
BILIKIN
LLNL
ATWC
PTWC
AVO
NMT
GEOSCOPE
PRSN
CISNUNR
LDEO
AEIC
CERI
MEDNET
GEOFON
Need auto QC methods for contributedNeed auto QC methods for contributed
stations to improve NEIC productsstations to improve NEIC products
Instrument Responses
IRIS DMC
Currently manual inspection methods are used to assurequality of GSN and ANSS backbone data and meta-data.
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NEIC Auto QC: Continuous Noise MonitoringProbability Density Function
Instrument Response
Gain, poles, zeros
calibration
Telemetry Issues
Gaps, drop-outs, dead channel System Transients
Mass recenters, spikes, clips
Vault performance
Pad tilt
Diurnal/seasonal variations
Cultural Noise Sources
Local machinery
Roads
ships
Network capability modeling
Detection threshold
Detection time
location error
14 day Probability Density Function constructed
with 672 individual PSDs, in 1/8 octave period and
1dB bins.
PDF Advantages:
earthquakes
Telemetry gaps
Canal LPnoise
microseism
Human activity
Barro Colorado, Panama (BCIP BHZ)
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PDF MethodData Prep:
1-hour time segments continuously
extracted from NEIC CWB, overlapping
by 50% (30 min.).
trend and mean removal
10% cos taper applied
No screening for earthquakes, or
transients and instrumental glitches such
as data gaps, clipping, spikes, mass re-
centers or calibration pulses
McNamara, D. E. and R.P. Buland, Ambient Noise Levels in the ContinentalUnited States, Bull. Seism. Soc. Am., 94, 4, 1517-1527, 2004.
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PSD calculatedfor each 1 hoursegmentWith ASLalgorithm for
direct comparisonto LNM.
PSD is smoothedby averagingpowers overfull octaves in1/8 octaveintervals.
Center points ofaverages shown.
LNM and HNM: Peterson (1993)
PDF Method: 1 hour
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PDF Method: 2 hours
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PDF Method: 1 day, 48 hours
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PDF Method: 1 week, 336 hours
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PDF Method: 2 weeks, 672hours
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PDF Method: 2 weeks, 672hours
Count PSD intersections per bin and normalize by total number of PSDs.
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PDF Method: 2 weeks, 672hours
14 day Probability Density Function constructed with 672 individual
PSDs, in 1/8 octave period and 1dB bins.
earthquakes
Telemetry gaps
Canal LPnoise
microseismHuman activity
Barro Colorado, Panama (BCIP BHZ)
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Boaz Consulting
IRIS - Data Management Center, Seattle, WA
IRIS - PASSCAL Instrument Center, Socorro, NM
National Science Foundation, Washington, D.C.United States Geological Survey - Golden, CO
PQLX
compute PDFs
build PSD database
graphically investigatetime series and PDFs
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NEIC Auto-QC: Detects matches and outliers
Reference models
Petersen High and Low Noise Models
- define standard operating range
Station Specific Noise Models- define station noise conditions
Noise Source Models- define station specific transients
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Petersen High and Low Noise ModelsHNM - defined by noisey GSN island stationsLNM - defined by quiet GSN continental stations
Tegucigalpa, Honduras, CU TEIG
Peterson, Observation and modeling of seismic background noise,U.S. Geol. Surv. Tech. Rept., 93-322, 1-95, 1993
P-waves Surface wavesSurface waves
BHZ LHZ
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Station Models - 10th and 90th percentiles of PDF distribution- define station ambient noise conditions
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Station Model Examples
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Bad Units input units
Displacement Instead of Velocity
Missing zero in Response File
Results in CW rotated PSD: High Amps at Low Period Low Amps at High Period
Corrected Response
PDF Instrument Response Sensitivity
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Bad STS2 Gain
Used 20,000 Volts/(m/s)Instead of 1500 Volts/(m/s)
Resulting in low correctedPower across spectrum.
Corrected Response
PDF Instrument Response Sensitivity
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60 day PDF US LRAL BHZ
STS2 auto re-center
seconds
Time series
Noise Source Modelsuse PQLX software to define station
specific transients and noise conditions
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60 day PDF US MSO BHZ
Calibration pulse
seconds
Time series
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60 day PDF AK MCK BHZ
Short data gaps
seconds
Time series
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Large Gaps
On-stops
Cultural noiseDiurnal Variations
Surface waves
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Detector Example: CU BCIP BHZ
1 hour PSD
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PSD fits within station model and HNM, LNM
match if 75% fit
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Detector Example: CU BCIP BHZ
1 hour PSD
No match if
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Detector Example: CU BCIP BHZ
1 hour PSD
calibration
No match if
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Detector Example: CU BCIP BHZ
1 hour PSD
Large gaps No match if
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Detector Example: CU BCIP BHZ
1 hour PSD
Small gaps
No match if
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Detector Example: CU BCIP BHZ
1 hour PSDSTS2 re-center
match if 75% fit
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Detector Example: CU BCIP BHZ
1 hour PSDSmall gaps
match if 75% fit
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Detector Example: CU BCIP BHZ
1 hour PSD
Small gaps
No match if
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In Summary
Auto-QC semi-operational at USGS NEIC- building DB of continuous hourly PSDs- daily inspection of PDFs with PQLX- daily computation of total station models- hand defined many noise models with
PQLX - daily stats on PSD matches and outliers
Further Development- additional noise sources from outliers- fine tune sensitivity parameters- PQLX enhancements- publish PDFs and stats to WWW
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Multi-Platform: Linux, MAC OS, Solaris
Source code for PQLX is freely available for download via WWW from:(source code managed using SVN)
http://wush net/svn/PQLX/tars
username = PQLXtars
password = getPQLX
Publicly Available, and Fully Searchable, Website for BugReporting and Enhancement Requests:
http://wush net/bugzilla/PQLX
PQLX Software
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